Rodrigo Sicarelli — Staff Software Engineer, Kotlin Multiplatform authority, speaker and OSS maintainer.https://rsicarelli.com/enhttps://rsicarelli.com/en/blog/kotlin-multiplatform-in-production/https://rsicarelli.com/en/blog/kotlin-multiplatform-in-production/What it actually takes to ship Kotlin Multiplatform across iOS and Android in a real product.Fri, 15 May 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/claude-code-101-demystifying-language-models/https://rsicarelli.com/en/blog/claude-code-101-demystifying-language-models/In the previous article, we built the entire factory: the evolution from manual production to autonomous machines, the ecosystem of agentic tools, the…Thu, 09 Apr 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/claude-code-101-introduction-to-agentic-programming/https://rsicarelli.com/en/blog/claude-code-101-introduction-to-agentic-programming/September 2025. I was leading a critical dependency upgrade on a mobile app with millions of users. The kind of change that breaks tests in a cascade.…Mon, 06 Apr 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/fakt-automating-the-fake-over-mock-pattern-amh/https://rsicarelli.com/en/blog/fakt-automating-the-fake-over-mock-pattern-amh/Kotlin testing has a problem that gets worse the more successful your project becomes.Wed, 25 Feb 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/the-hidden-cost-of-default-hierarchy-templates-in-kotlin-multiplatform/https://rsicarelli.com/en/blog/the-hidden-cost-of-default-hierarchy-templates-in-kotlin-multiplatform/The Default Hierarchy Template in KMP projects is a great way to reduce boilerplate code and start working quickly. However, it came with an unexpected…Sun, 02 Nov 2025 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-modularizacao-no-kmp/https://rsicarelli.com/en/blog/kmp-102-modularizacao-no-kmp/In the last article we dug into the quirks of code exported to Objective-C headers, along with the best practices for what to export…Fri, 07 Mar 2025 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-otimizando-a-exportacao-do-kotlin-para-o-obj-cswift/https://rsicarelli.com/en/blog/kmp-102-otimizando-a-exportacao-do-kotlin-para-o-obj-cswift/In the last post, we learned how to use Kotlin code in Swift, some techniques to improve the code exported to Swift, and how annotations control its…Sat, 18 Jan 2025 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-utilizando-codigo-kotlin-no-swift/https://rsicarelli.com/en/blog/kmp-102-utilizando-codigo-kotlin-no-swift/In the last post, we learned how to create an XCFramework from Kotlin code and explored some characteristics of the generated build types.Fri, 11 Oct 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-caracteristicas-do-xcframework-no-kmp/https://rsicarelli.com/en/blog/kmp-102-caracteristicas-do-xcframework-no-kmp/In the previous post, we learned how Kotlin/Native exports a collection of .frameworks in the XCFramework format.Sun, 21 Jul 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-xcframework-para-devs-kmp/https://rsicarelli.com/en/blog/kmp-102-xcframework-para-devs-kmp/Welcome to the KMP-102 series. We dig deeper into Kotlin Multiplatform concepts, learning more about how to integrate our Kotlin code into iOS and beyond.Wed, 29 May 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-alias-para-importacao-import-alias/https://rsicarelli.com/en/blog/kotlin-koans-br-alias-para-importacao-import-alias/When importing a class or function, you can give it a different name by adding as NewName after the import directive. This can be useful when…Sat, 06 Apr 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-extension-functions-e-properties-funcoes-e-propriedades-estendidas/https://rsicarelli.com/en/blog/kotlin-koans-br-extension-functions-e-properties-funcoes-e-propriedades-estendidas/Implement the extension functions Int.r() and Pair.r() so they convert an Int and a Pair into a RationalNumber.Sat, 06 Apr 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-nomeados/https://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-nomeados/Make the joinOptions() function return the list in JSON format (for example, [a, b, c]) by specifying only two arguments.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-padrao/https://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-padrao/Imagine you have several overloads of foo() in your favorite language. You can replace them all with a single function in Kotlin.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-classes-de-dados-data-classes/https://rsicarelli.com/en/blog/kotlin-koans-br-classes-de-dados-data-classes/Rewrite the following code in Kotlin, then add the data modifier. A beginner-friendly look at Kotlin classes and data classes.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-classes-seladas/https://rsicarelli.com/en/blog/kotlin-koans-br-classes-seladas/Reuse your solution from the previous task, but replace the interface with a sealed interface. That way you no longer need the else branch in the when expression.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-lambdas/https://rsicarelli.com/en/blog/kotlin-koans-br-lambdas/Pass a lambda to the any function to check whether the collection contains an even number.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-modelos-de-string/https://rsicarelli.com/en/blog/kotlin-koans-br-modelos-de-string/The pattern below matches a date in the format 13.06.1992 (two digits, a dot, two digits, a dot, four digits):Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-ola-mundo/https://rsicarelli.com/en/blog/kotlin-koans-br-ola-mundo/Change the code so that the start function returns the string "OK".Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-strings-com-tres-aspas/https://rsicarelli.com/en/blog/kotlin-koans-br-strings-com-tres-aspas/Swap the trimIndent call for trimMargin, setting # as the prefix value, so the resulting string no longer contains the prefix character.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-tipagem-inteligente/https://rsicarelli.com/en/blog/kotlin-koans-br-tipagem-inteligente/Rewrite the given code using Kotlin smart casts and the when expression.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-tipo-nenhum-nothing/https://rsicarelli.com/en/blog/kotlin-koans-br-tipo-nenhum-nothing/Specify the Nothing return type for the failWithWrongAge function.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-tipos-anulaveis/https://rsicarelli.com/en/blog/kotlin-koans-br-tipos-anulaveis/Rewrite the following code so that it uses only a single if expression, and learn how Kotlin handles nullable types safely.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-explorando-as-dependencias-internas-e-externas-no-kmp/https://rsicarelli.com/en/blog/kmp-101-explorando-as-dependencias-internas-e-externas-no-kmp/In previous articles, we established a foundation in Kotlin Multiplatform (KMP) and how it compiles to multiple platforms.Sat, 27 Jan 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-como-compartilhar-codigo-no-kmp-conectando-plataformas-com-expect-e-actual/https://rsicarelli.com/en/blog/kmp-101-como-compartilhar-codigo-no-kmp-conectando-plataformas-com-expect-e-actual/Unpacking the expect and actual keywords in Kotlin Multiplatform and the different ways they let you share code across platforms.Wed, 13 Dec 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-aprendendo-sobre-o-uso-do-gradle-no-kotlin-multiplataforma/https://rsicarelli.com/en/blog/kmp-101-aprendendo-sobre-o-uso-do-gradle-no-kotlin-multiplataforma/In the last article, we created a project using the KMP Wizard and, with little effort, ran our app on Android, iOS, and Desktop.Fri, 01 Dec 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-criando-e-executando-seu-primeiro-projeto-multiplataforma-no-fleet/https://rsicarelli.com/en/blog/kmp-101-criando-e-executando-seu-primeiro-projeto-multiplataforma-no-fleet/Over the last few articles we covered key KMP concepts, from the multiplatform paradigm to setting up the environment.Fri, 01 Dec 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-guia-pratico-para-configurar-e-entender-o-ambiente-no-kotlin-multiplataforma/https://rsicarelli.com/en/blog/kmp-101-guia-pratico-para-configurar-e-entender-o-ambiente-no-kotlin-multiplataforma/Software development is a complex process that demands not only skill and creativity, but also a well-configured development environment.Wed, 29 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-multiplataforma-101-dominando-os-principios-dos-source-sets/https://rsicarelli.com/en/blog/kotlin-multiplataforma-101-dominando-os-principios-dos-source-sets/In the last article, we learned about the Kotlin compiler frontend, IR, and backend. Now we dig into source sets — the key concept for writing KMP code.Fri, 24 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-multiplataforma-101-entendendo-como-o-kotlin-compila-para-multiplas-plataformas/https://rsicarelli.com/en/blog/kotlin-multiplataforma-101-entendendo-como-o-kotlin-compila-para-multiplas-plataformas/In the last post (🔗 KMP 101: An Introduction to the multiplatform paradigm), we explored the multiplatform paradigm and how KMP stands out in the ecosystem.Tue, 21 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-multiplataforma-101-introducao-ao-paradigma-da-multiplataforma/https://rsicarelli.com/en/blog/kotlin-multiplataforma-101-introducao-ao-paradigma-da-multiplataforma/We use a wide range of apps every day on phones, watches, TVs, and computers, all part of a broad digital ecosystem.Tue, 14 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-0-introducao-a-serie/https://rsicarelli.com/en/blog/android-plataforma-parte-0-introducao-a-serie/Android development is a constant stream of new devices, SDK updates, and a flood of libraries and tools shipping every day. Here is how we tame it.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-1-modularizacao/https://rsicarelli.com/en/blog/android-plataforma-parte-1-modularizacao/Efficiency matters in modern software projects. This article covers modularization in Kotlin/Android projects, Gradle, and the challenges of many modules.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-10-customizacao-dos-modulos/https://rsicarelli.com/en/blog/android-plataforma-parte-10-customizacao-dos-modulos/In the last article we explored CommonsExtension to remove duplication from our configuration.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-11-criando-uma-dsl-para-customizar-as-novas-opcoes/https://rsicarelli.com/en/blog/android-plataforma-parte-11-criando-uma-dsl-para-customizar-as-novas-opcoes/In the previous article, we parameterized the arguments of applyAndroidApp() and appyAndroidLibary() with models.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-12-otimizando-tempo-de-compilacao-para-bibliotecas-android/https://rsicarelli.com/en/blog/android-plataforma-parte-12-otimizando-tempo-de-compilacao-para-bibliotecas-android/🌱 Branch: 12/improving-android-library-build-time 🔗 Repository:...Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-13-incluindo-modulos-puro-jvm/https://rsicarelli.com/en/blog/android-plataforma-parte-13-incluindo-modulos-puro-jvm/In the last article we sped up Android module builds by turning off several Android Gradle Plugin (AGP) features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-14-aderindo-a-funcionalidades-experimentais-do-compilador-do-kotlin/https://rsicarelli.com/en/blog/android-plataforma-parte-14-aderindo-a-funcionalidades-experimentais-do-compilador-do-kotlin/In the last article we extended our platform with the ability to declare JVM modules.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-15-cuidando-do-codigo-com-detekt-klint-e-spotless/https://rsicarelli.com/en/blog/android-plataforma-parte-15-cuidando-do-codigo-com-detekt-klint-e-spotless/In the last article we covered how our platform lets different modules opt into experimental features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-16-consideracoes-finais/https://rsicarelli.com/en/blog/android-plataforma-parte-16-consideracoes-finais/Over the last articles, we built a platform from scratch, learning and applying concepts to make multi-module Kotlin apps more flexible and scalable.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-2-inicio-do-projeto/https://rsicarelli.com/en/blog/android-plataforma-parte-2-inicio-do-projeto/In this post we explore a starter project, understand the challenges of maintaining build.gradle.kts files, and discover how Gradle Composite Builds…Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-3-compartilhando-scripts-do-gradle/https://rsicarelli.com/en/blog/android-plataforma-parte-3-compartilhando-scripts-do-gradle/In the previous article we saw the challenges of a multi-module project: maintaining and reusing Gradle files. Let us dig into how to solve that.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-4-composite-build-lgk/https://rsicarelli.com/en/blog/android-plataforma-parte-4-composite-build-lgk/In the previous articles we saw why modularity matters and why Composite Builds are the right choice for scaling Kotlin projects.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-5-simplificando-gradle-init/https://rsicarelli.com/en/blog/android-plataforma-parte-5-simplificando-gradle-init/In the previous article, we set up our platform with build-logic and registered the greeting task in the main project.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-6-version-catalog/https://rsicarelli.com/en/blog/android-plataforma-parte-6-version-catalog/In the previous post, we optimized our platform and got it ready for more features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-7-decorando-o-modulo-app/https://rsicarelli.com/en/blog/android-plataforma-parte-7-decorando-o-modulo-app/In the previous article, we got our platform ready to take on new features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-8-decorando-os-modulo-library/https://rsicarelli.com/en/blog/android-plataforma-parte-8-decorando-os-modulo-library/In the last post, we introduced the first decoration in the Platform and set up our entire app module using the Kotlin DSL.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-9-unificando-a-application-e-library-extensions-com-a-common-extension/https://rsicarelli.com/en/blog/android-plataforma-parte-9-unificando-a-application-e-library-extensions-com-a-common-extension/In the last post, we managed to extract the configuration logic for our library modules.Wed, 27 Sep 2023 00:00:00 GMT